Evaluation, validation and business analysis of ethanol production from alternative substrates using BIOTECH yeast strains

About 115 locally isolated yeast strains were screened to identify the top 10 ethanol producer for each of the commonly used conventional feedstocks/substrates (molasses, sugarcane juice, sweet sorghum juice and cassava). The ethanol production of these isolates in flask fermentation were compared with HBY3 and industrial strain (now used in the industry) also isolated by BIOTECH [UPLB-National Inst. of Molecular Biology and Biotechnology]. The top strains for each feedstock were different indicating that there may be a best strain for a particular feedstock. Moreover, the final ethanol concentration of the top strains were at least 1% higher than HBY3. Bioreactor studies were performed to further determine the batch fermentation kinetics of the top BIOTECH yeast strains from the flask fermentation studies. Results showed the top BIOTECH yeasts performed better (in terms of higher ethanol produced, specific ethanol productivity, fermentation efficiency), compared with the BIOTECH industrial HBY3 strain in sugarcane syrup and sweet sorghum syrup. For both feedstocks, strain 2013 was the top performer with fermentation efficiency of 93.1% and 90.4% in sugarcane syrup and sweet sorghum syrup, respectively. These values are higher than the 78.0% and 82.4% fermentation efficiencies of HBY3 in sugarcane and sweet sorghum syrup, respectively. HBY3, however, performed slightly better than the other BIOTECH isolates in cassava starch hydrolysate. Repeated Batch Fermentation was also conducted using one of the top yeast strains which resulted in higher ethanol productivity of ethanol fermentation using molasses. More studies should also be conducted using other feedstocks. The top yeast isolates were subjected to molecular characterization and finger printing before the validation trials in actual distillery conditions. The procedure confirmed that indeed the isolates were distinct yeast strains. The performance validation BIOTECH yeast strain 2013 and 2014 in actual distillery conditions were conducted using molasses substrate at Absolute Distillers Inc. (ADI). The overall performance of BIOTECH strains found to be comparable to that of the ADI strain. ADI was particularly impressed and see high potential in the industry for BIOTECH strain 2014, which achieved high cell density and high ethanol production in shorter period of time. These BIOTECH yeast strains can be competitive commercially because of its potential to reduce material inputs in every production runs of around 2.5 metric tons of molasses. The bottomline is that the distillery has the potential to generate annual savings of at least PhP672,000.00 if it will adopt the new BIOTECH strains. More validation trials is recommended to extensively validate the performance and potential of BIOTECH strains during actual runs using various feedstocks and other fermentation systems.